The invention relates to a method of sterilizing endoscopes and in particular hollow endoscopes.
The development of endoscopic instruments has greatly advanced the ability of the medical profession to diagnose and treat diseases in relatively inaccessible regions of the body. The first examinations that could be considered xe2x80x9cendoscopicxe2x80x9d in the modern sense were probably the rectal inspections conducted in the 18th century. The physician peered through a rigid tube inserted into the patient""s rectum and relied on candles or gas lamps to illuminate the interior. By today""s standards the physician saw very little; however, endoscopic examinations continued and endoscopes of various designs were invented and have revolutionized many medical procedures.
As is well known to one skilled in the art, endoscope tubes often include mechanisms for turning the tip in four directions, up, down and from side to side, to facilitate passage of the instrument around angles and allow visualization of all surfaces. An additional viewing channel, coupled to a separate eye piece, for simultaneous direct viewing by a second observer is also available. In addition, the tubes contain channels for air insufflation and water instillation, so that lenses can be cleaned during a procedure, and to allow passage of biopsy instruments and fulguration instruments. Tube channels may also be provided for passage of light from a laser for ablation/photo dynamic therapy, spray catheters, polypectomy snare wires etc.
A typical endoscope, as found in a physician""s office or hospital, is used repeatedly. Thus, it is imperative that endoscopic tubes must be completely sterilized between each use to avoid the transmission of diseases, such as AIDS, Hepatitis, etc. Typically, a sterilization fluid is passed through the water and air ducts of the instrument to sterilize the internal surfaces. This sterilization fluid is at times supplied from a bottle which temporarily replaces the water bottle used with the endoscope. As is evident to one skilled in the art, conduits (internal surfaces) within the endoscope are the most difficult parts of the endoscope to sterilize. Endoscopic materials are also often heat sensitive and do not lend themselves to heat sterilization techniques.
In light of the ubiquitous use of the endoscope by the medical profession and intricate internal surfaces of the endoscope, an efficient method for sterilizing the endoscope at ambient temperatures is required.
U.S. Pat. No. 4,862,872 issued to Yabe et al. on Sep. 5, 1989 discloses an endoscope and a washing apparatus for an endoscope. The endoscope comprises an elongate insertable part having an observation window and illuminating window in the tip part, an observation means for observing an object by receiving a returning light from the object which enters through the observing window, an illuminating light output means emitting an illuminating light from the illuminating window and a memorizing means capable of memorizing the information on washing. The washing apparatus is provided with a read-out means for reading out the information memorized by the memorizing means of the above mentioned endoscope and a control means controlling the conditions of washing the above mentioned endoscope by the information read out by this read-out means. This endoscope washing apparatus is relatively complex and likely expensive to manufacture.
U.S. Pat. No. 5,297,537 issued to Savitt et al. on Mar. 29, 1994 discloses a disposable liquid supply kit for use with an endoscope that comprises a closed liquid container for connection to an endoscope prior to use. With a disposable unit of this type, a fresh supply of sterile water is installed in the endoscope between each use with a patient. The liquid supply system is preferably sealed at the factory to insure complete sterilization. Obviously, a medical facility using such a kit requires inventory and incurs expense as a result of maintaining and monitoring the inventory.
U.S. Pat. No. 5,534,221 issued to Hillebrenner et al. on Jul. 9, 1996 entitled xe2x80x9cDevice and system for sterilizing objectsxe2x80x9d discloses a hollow cassette for holding an item to be sterilized, for example an endoscope. The cassette is a sealable cassette in which an endoscope or other medical device is placed. The cassette has input and output fluid sealing ports for the introduction and removal of a sterilizing fluid. The cannula of the endoscope is coupled either to the input or output port. The cassette is formed of two identical halves which are placed in superimposed sealable relationship with each other to form a hollow chamber. A latch is placed on one or more handles on the cassette to create a presealing condition to allow a vacuum to be introduced at the outlet port. The cassette is then placed in an outer oven-like container or warming chamber where the temperature is properly maintained. Connections are made to open the input and output ports on the cassette such that the sterilizing agent may be introduced through a first port to bathe the outside of the medical endoscope, while one end of the endoscope is coupled to the output port where a vacuum is supplied external to the cassette to pull the sterilization agent into the cassette and through the interior passageways of the endoscope. When the sterilization process is completed, the warming chamber is opened and the sterilizing cassette is simply removed from the chamber with the input and output ports being uncoupled from their respective sources. A tight seal is maintained and the object remains in the sterilized interior of the cassette until the cassette is opened or the device is to be used. This represents a sterilization system which is relatively costly to produce and use.
It would be advantageous to provide a method for endoscopic sterilization that is inexpensive and operatively simple. It would also be advantageous to provide a method that can be used with a sterilizing chamber that is used to sterilize many different articles and not just for endoscopic sterilization per se. It has now been found that by applying principles of pressure equilibration it is possible for an endoscope""s conduit(s) and external surfaces to be sterilized.
Conventional sterilization procedures for medical instruments involve high temperature (such as steam and dry heat units) or toxic chemicals (such as ethylene oxide gas, EtO). Steam pressure sterilization has been the time-honoured method of sterilization. It is fast and cost effective. However, the autoclave destroys heat-sensitive instruments such as arthroscopes and endoscopes.
Ethylene oxide sterilization is used to cold-sterilize heat-sensitive instruments and can be used as a sterilization gas. However, it has been deemed by national health and safety organizations to be carcinogenic and neurotoxic, and requires long sterilization and aeration periods.
Ozone is a more efficient, safer, and less expensive sterilization agent and is easily generated from oxygen, preferably hospital grade oxygen. Ozone is widely used in industry as an oxidising agent to bleach paper pulp, treat drinking water, and sterilize sewage water and food products. Ozone generally acts on chemical compounds in two ways. Either by direct reaction or through hydroxyl radical species formed during the decomposition of ozone (Encyclopaedia Of Chemical Technology, Vol. 17, Ozone page 953 to 964). The amounts (concentrations) of ozone required in the sterilization gas for water purification are low, generally less than 36 mg/l (milligram per liter). Significantly higher concentrations are required to make ozone gas an effective sterilant of micro-organisms, and those high concentrations of ozone gas are generally combined with critical levels of humidity during the entire sterilization cycle to improve sterilization efficiency. The activity of ozone increases rapidly with increased relative humidity. The resistance of spores to ozone varies from strain to strain, but the differences become comparatively small at high relative humidity (Ishizaki et al., 1986. Inactivation of the Silas spores by gaseous ozone, J. Appl Bacterial, 60:67-72), a high relative humidity is required for the ozone to penetrate the protective shells of micro-organisms. The presence of water often accelerates ozone reactions with organic substances (Langlais et al., (EDS), 1991, Ozone in Water Treatment, Application and Engineering. Louis Publishers: Chelsea, Mich., 569 pages). Thus, ozone containing gas can also be used as a sterilizing agent for endoscopes, especially when combined with high humidity.
Water evaporates at 100xc2x0 C. at atmospheric pressure (1013 mbar). Thus, various prior patents (see Faddis et al., U.S. Pat. Nos. 5,266,275; 5,334,355; and 5,334,622) teach sterilization systems wherein water is heated to above the boiling point (100xc2x0 C. at 1013 mbar) to evaporate the water for injection into the ozone-containing gas produced by an ozone generator. The steam is heated to 120xc2x0 C. prior to injection into the ozone-containing gas. However, since the decomposition of ozone increases exponentially with temperature in the range of 20 to 300xc2x0 C., injecting the water vapour at a temperature of about 120xc2x0 C. leads to premature ozone decomposition. A more efficient and effective sterilization apparatus for the sterilization of ozone at a relative humidity above at least 95% is disclosed in our co-pending U.S. patent application Ser. No. 09/310,695 which is incorporated herein in its entirety.
It is an object of the present invention to provide a method for the sterilization of a hollow endoscope.
It is another object of the invention to provide a sterilization method for an endoscope in which the sterilization is carried out with a sterilizing gas, for example an ozone-containing gas, preferably humidified ozone-containing gas, having a temperature of 20xc2x0 C. to 35xc2x0 C.
Endoscopes are available that do not have passages through which a fluid may pass. Nevertheless, the majority of endoscopes have at least one passage through the endoscope. The present invention provides a method of sterilizing endoscopes with internal passages, i.e., hollow endoscopes.
As one skilled in the art will appreciate, it is possible to disassemble an endoscope into sections. Methods for sterilizing an xe2x80x9cendoscopexe2x80x9d as disclosed herein are applicable to both assembled endoscopes and sections thereof. Hence, the term xe2x80x9cendoscopexe2x80x9d as used herein is to be construed as encompassing hollow endoscope sections.
In accordance with the present invention there is provided a method for sterilizing within a sterilization chamber a hollow endoscope having an internal passage having an internal volume comprising the steps of:
(i) sealing the endoscope to a sealed vessel for fluid communication between the passage and the vessel to form an endoscope-vessel combination, said vessel having an internal volume;
(ii) disposing the endoscope-vessel combination within the sterilization chamber;
(iii) supplying a sterilization gas;
(iv) effecting a pressure difference between the internal volume of the vessel and the sterilizing chamber, the pressure in the sterilizing chamber and the internal volume of the vessel selected such that sterilizing gas supplied to the sterilizing chamber flows through the internal passage of the endoscope into the vessel.
Preferably the end of the endoscope which is sealed in fluid communication with said vessel, protrudes into said vessel.
In accordance with a further preferred embodiment of the present invention there is provided a method for sterilizing within a sterilization chamber a hollow endoscope having a distal end, a proximal end and an internal passage having an internal volume comprising the steps of:
(i) providing a sterilization chamber;
(ii) sealing the distal end of the endoscope in fluid communication with a substantially closed vessel to form an endoscope-vessel combination, said vessel having an internal volume larger than the internal volume of the endoscope;
(iii) placing the endoscope-vessel combination into the sterilization chamber;
(iv) sealing the sterilization chamber;
(v) applying a vacuum of a preselected vacuum pressure to the sterilization chamber;
(vi) supplying an amount of water vapour to the sterilization chamber for humidifying the sterilization chamber;
(vii) supplying ozone to the sterilizing chamber at a higher pressure than said pre-selected vacuum pressure, said ozone being sufficient to sterilize the endoscope and the internal passage of the endoscope; and
(viii) maintaining the endoscope, the internal volume of the endoscope and the internal volume of the vessel in contact with the ozone for a preselected treatment period to sterilize the endoscope